uTools-Manuals/docs/javascript/Reference/Global_Objects/isFinite.html

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<p>该全局 <strong><code>isFinite()</code></strong> 函数用来判断被传入的参数值是否为一个有限数值（finite number）。在必要情况下，参数会首先转为一个数值。</p>
<div><iframe class="interactive interactive-js" frameborder="0" height="250" src="https://interactive-examples.mdn.mozilla.net/pages/js/globalprops-isfinite.html" width="100%"></iframe></div>
<h2 id="语法">语法</h2>
<pre><code class="language-html" style="margin-bottom: 0px; padding: 1em; border-left-width: 6px; border-left-style: solid; font-family: Consolas, Monaco, 'Andale Mono', monospace; font-size: 14px; direction: ltr; white-space: normal; text-shadow: none; background-color: rgba(212, 221, 228, 0.498039);">isFinite(<em>testValue</em>)</code></pre>
<h3 id="Parameters" name="Parameters">参数</h3>
<dl>
<dt><code>testValue</code></dt>
<dd>用于检测有限性（finiteness）的值。</dd>
</dl>
<h3 id="Description" name="Description">描述</h3>
<dl>
<dd>isFinite 是全局的方法，不与任何对象有关系。</dd>
</dl>
<p>你可以用这个方法来判定一个数字是否是有限数字。<code>isFinite</code> 方法检测它参数的数值。如果参数是 <code>NaN</code>，正无穷大或者负无穷大，会返回<code>false</code>，其他返回 <code>true</code>。</p>
<h2 id="Examples" name="Examples" style="margin-bottom: 20px; line-height: 30px;">示例</h2>
<pre><code class="language-js language-js" style="padding: 1em 0px 1em 30px; border-left-width: 6px; border-left-style: solid; font-family: Consolas, Monaco, 'Andale Mono', monospace; font-size: 14px; direction: ltr; white-space: normal; text-shadow: none; background-color: rgba(234, 239, 242, 0.247059);"><code class="language-js" style="font-family: Consolas, Monaco, 'Andale Mono', monospace; direction: ltr; white-space: pre; color: inherit; text-shadow: none;"><span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="number token" style="color: #990055;">Infinity</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span> <span class="comment token" style="color: #708090; display: inherit;"> // false
</span><span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="number token" style="color: #990055;">NaN</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span>      <span class="comment token" style="color: #708090; display: inherit;"> // false
</span><span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="operator token" style="background: rgba(255, 255, 255, 0.498039); color: #a67f59;">-</span><span class="number token" style="color: #990055;">Infinity</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span><span class="comment token" style="color: #708090; display: inherit;"> // false
</span>
<span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="number token" style="color: #990055;">0</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span>        <span class="comment token" style="color: #708090; display: inherit;"> // true
</span><span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="number token" style="color: #990055;">2e64</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span>     <span class="comment token" style="color: #708090; display: inherit;"> // true, 在更强壮的Number.isFinite(null)中将会得到false
</span>

<span class="function token">isFinite<span class="punctuation token" style="color: #999999;">(</span></span><span class="string token" style="color: #669900;">"0"</span><span class="punctuation token" style="color: #999999;">)</span><span class="punctuation token" style="color: #999999;">;</span>      <span class="comment token" style="color: #708090; display: inherit;"> // true, 在更强壮的Number.isFinite('0')中将会得到false</span></code></code></pre>
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<h2 id="规范" style="margin-bottom: 20px; line-height: 30px;">规范</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/publications/files/ECMA-ST-ARCH/ECMA-262,%203rd%20edition,%20December%201999.pdf" hreflang="en" lang="en" rel="noopener" title="ECMAScript 3rd Edition (ECMA-262)">ECMAScript 3rd Edition (ECMA-262)</a></td>
<td><span class="spec-Standard">Standard</span></td>
<td>Initial definition.</td>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/5.1/#sec-15.1.2.5" hreflang="en" lang="en" rel="noopener">ECMAScript 5.1 (ECMA-262)<br/><small lang="zh-CN">isFinite</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-isfinite-number" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">isFinite</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
</tr>
<tr>
<td><a class="external" href="https://tc39.github.io/ecma262/#sec-isfinite-number" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">isFinite</small></a></td>
<td><span class="spec-Draft">Draft</span></td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性" style="margin-bottom: 20px; line-height: 30px;">浏览器兼容性</h2>
<p></p><div class="bc-data"><a class="bc-github-link external" href="https://github.com/mdn/browser-compat-data" rel="noopener">Update compatibility data on GitHub</a><table class="bc-table bc-table-js"><thead><tr class="bc-platforms"><td></td><th class="bc-platform-desktop" colspan="6"><span>Desktop</span></th><th class="bc-platform-mobile" colspan="7"><span>Mobile</span></th><th class="bc-platform-server" colspan="1"><span>Server</span></th></tr><tr class="bc-browsers"><td></td><th class="bc-browser-chrome"><span class="bc-head-txt-label bc-head-icon-chrome">Chrome</span></th><th class="bc-browser-edge"><span class="bc-head-txt-label bc-head-icon-edge">Edge</span></th><th class="bc-browser-firefox"><span class="bc-head-txt-label bc-head-icon-firefox">Firefox</span></th><th class="bc-browser-ie"><span class="bc-head-txt-label bc-head-icon-ie">Internet Explorer</span></th><th class="bc-browser-opera"><span class="bc-head-txt-label bc-head-icon-opera">Opera</span></th><th class="bc-browser-safari"><span class="bc-head-txt-label bc-head-icon-safari">Safari</span></th><th class="bc-browser-webview_android"><span class="bc-head-txt-label bc-head-icon-webview_android">Android webview</span></th><th class="bc-browser-chrome_android"><span class="bc-head-txt-label bc-head-icon-chrome_android">Chrome for Android</span></th><th class="bc-browser-edge_mobile"><span class="bc-head-txt-label bc-head-icon-edge_mobile">Edge Mobile</span></th><th class="bc-browser-firefox_android"><span class="bc-head-txt-label bc-head-icon-firefox_android">Firefox for Android</span></th><th class="bc-browser-opera_android"><span class="bc-head-txt-label bc-head-icon-opera_android">Opera for Android</span></th><th class="bc-browser-safari_ios"><span class="bc-head-txt-label bc-head-icon-safari_ios">Safari on iOS</span></th><th class="bc-browser-samsunginternet_android"><span class="bc-head-txt-label bc-head-icon-samsunginternet_android">Samsung Internet</span></th><th class="bc-browser-nodejs"><span class="bc-head-txt-label bc-head-icon-nodejs">Node.js</span></th></tr></thead><tbody><tr><th scope="row"><code>isFinite</code></th><td class="bc-supports-yes bc-browser-chrome"><span class="bc-browser-name">Chrome</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-edge"><span class="bc-browser-name">Edge</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-firefox"><span class="bc-browser-name">Firefox</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              1</td><td class="bc-supports-yes bc-browser-ie"><span class="bc-browser-name">IE</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-opera"><span class="bc-browser-name">Opera</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-safari"><span class="bc-browser-name">Safari</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-webview_android"><span class="bc-browser-name">WebView Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-chrome_android"><span class="bc-browser-name">Chrome Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-edge_mobile"><span class="bc-browser-name">Edge Mobile</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-firefox_android"><span class="bc-browser-name">Firefox Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              4</td><td class="bc-supports-yes bc-browser-opera_android"><span class="bc-browser-name">Opera Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-safari_ios"><span class="bc-browser-name">Safari iOS</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-samsunginternet_android"><span class="bc-browser-name">Samsung Internet Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-nodejs"><span class="bc-browser-name">nodejs</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td></tr></tbody></table><section class="bc-legend" id="sect1"><h3 class="offscreen" id="Legend">Legend</h3><dl><dt><span class="bc-supports-yes bc-supports">
<abbr class="bc-level bc-level-yes only-icon" title="Full support">
<span>Full support</span>
                  
                </abbr></span></dt><dd>Full support</dd></dl></section></div><p></p>
<h2 id="See_Also" name="See_Also" style="margin-bottom: 20px; line-height: 30px;">相关链接</h2>
<ul>
<li><a href="Reference/Global_Objects/Number/isFinite" title="Number.isFinite() 方法用来检测传入的参数是否是一个有穷数（finite number）。"><code>Number.isFinite()</code></a></li>
<li><a href="Reference/Global_Objects/Number/NaN" title="Number.NaN 表示“非数字”（Not-A-Number）。和 NaN 相同。"><code>Number.NaN()</code></a></li>
<li><a href="Reference/Global_Objects/Number/POSITIVE_INFINITY" title="Number.POSITIVE_INFINITY 属性表示正无穷大。"><code>Number.POSITIVE_INFINITY</code></a></li>
<li><a href="Reference/Global_Objects/Number/NEGATIVE_INFINITY" title="Number.NEGATIVE_INFINITY 属性表示负无穷大。"><code>Number.NEGATIVE_INFINITY</code></a></li>
</ul>
</article>